Chiller refrigerants

ABSTRACT

Disclosed is a nonflammable refrigerant composition consisting of pentafluoroethane in an amount from 62% to 67% based on the weight of the composition, a second component that is selected from 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, and mixtures thereof in an amount from 26% to 36% by weight; and an ethylenically unsaturated or saturated hydrocarbon compound that is at least 70% isobutane in an amount of from 1% to 4% by weight and up to 5% by weight based on the weight of the composition of another flurohydrocarbon. The composition optionally may further include at least one additive, lubricant or combination thereof.

This invention relates to refrigerant compositions, particularlycompositions which can be used for chillers. In particular, these aredevices for producing chilled water or aqueous solutions at temperaturestypically from 1 to 10° C.

Chillers require large amounts of cooling. Recently R22 (CHClF₂) hasbeen used for this purpose. However, there is the need for analternative refrigerant, since R22 is an ozone depleter that will bephased out over the next decade, in accordance with the Montrealprotocol.

Therefore, there is a requirement for a refrigerant that has similarproperties to R22, but is not an ozone depleter. Of particular concernis that the temperature/vapour pressure relationship for such arefrigerant should be sufficiently similar to R22 that it can be used inR22 equipment without having to change the control systems which areusually programmed in the factory making the chiller.

This is of particular concern for systems that have sensitive controldevices, which rely on both the inlet pressure to the expansion valveand the outlet pressure. These control systems are based on R22properties. Therefore, if an R22 substitute does not have atemperature/vapour pressure behavior similar to R22, the system will notoperate correctly.

By similar we mean that the vapour pressure of the substitute should notdiffer by more than ±12% and preferably not more than ±6% at any givenmean evaporating temperature between −40° C. to +10° C.

It Is also important that any such refrigerant has a similar capacityand efficiency as R22.

By similar capacity we mean a capacity that is n more than 20% lowerthan R22 and preferably not more than 10% lower than R22 at meanevaporating temperatures between −36° C. to −28° C. By similarefficiency we mean not more than 10% lower and preferably not more than5% lower at mean evaporating temperatures between −35 to −28° C.

According to the present invention there is provided a refrigerantcomposition which comprises:

-   -   (a) pentafluoroethane, trifluoromethoxydifluoromethane or        hexafluorocyclopropane, or a mixture of two or more thereof, in        an amount of from 60 to 70% by weight based on the weight of the        composition.    -   (b) 1,1,1,2- or 1,1,2,2-tetrafluoroethane,        trifluoromethoxypentafluoroethane,        1,1,1,2,3,3-heptafluoropropane or a mixture of two ore more        thereof, in an amount of from 26 to 36% by weight based on the        weight of the composition and    -   (c) an ethylenically unsaturated or saturated hydrocarbon,        optionally containing one or more oxygen atoms, with a boiling        point from −12° C. to +10° C., or a mixture thereof, or a        mixture of one or more said hydrocarbons with one or more other        hydrocarbons, said mixture having a bubble point from −12° C. to        +10° C., in an amount from 1% to 4% by weight based on the        weight of the composition. It has surprisingly been found that        these particular formulations have the condition of properties        which enable them to be used as a “drop in” replacement for R22.

The percentages quoted above refer, in particular, to the liquid phase.The corresponding ranges for the vapour phase are as follows: (a) 75 to87% (b) 10-28% and (c) 0.9-4.1%, all by weight based on the weight ofthe composition. These percentages preferably apply both in the liquidand vapour phases.

The present invention also provides a process for producingrefrigeration which comprises condensing a composition of the presentinvention and thereafter evaporating the composition in the vicinity ofa body to be cooled. The invention also provides a refrigerationapparatus containing, as refrigerant, a composition of the presentinvention.

Component (a) is present in an amount from 60 to 70% by weight based onthe weight of the composition. Preferably, the concentration is 62 to67%, especially above 64% and up to 66%, by weight. Preferably,component (a) is R125 (pentafluoroethane) or a mixture containing atleast a half, especially at least three quarters (by mass) of R125. Mostpreferably component (a) is R125 (alone).

Component (b) is present in the composition in an amount from 26 to 36%,especially 28 to 32%, by weight based on the weight of the composition.Component (b) is preferably a mixture containing at least a half,especially at least three quarters (by mass) of R134a(1,1,1,2-tetrafluoroethane). Most preferably component (b) is R134a(alone).

The weight ratio of component (a): component (b) is desirably at least1.5:1, preferably 1.5:1 to 3:1 and especially 1.8:1 to 2.2:1.

Component (c) is a saturated or ethylenically unsaturated hydrocarbon,optionally containing one or more oxygen atoms, in particular one oxygenatom, with a boiling point from −12° C. to −10° C., especially −12° C.to −5° C. or a mixture thereof. Preferred hydrocarbons which can be usedpossess three to five carbon atoms. They can be acyclic or cyclic.Acyclic hydrocarbons which can be used include one or more of propane,n-butane, isobutane, and ethylmethyl ether. Cyclic hydrocarbons whichcan be used include methyl cylclo propane. Preferred hydrocarbonsinclude n-butane and/or isobutane. Component (c) can also be a mixtureof such a hydrocarbon with one or more other hydrocarbons, said mixturehaving a bubble point from −12° C. to −10° C., especially −12° C. to −5°C. Other hydrocarbons which can be used in such mixtures include pentaneand isopentane, propene, dimethyl ether, cyclobutane, cyclopropane andoxetan.

The presence of at least one further component in the composition is notexcluded. Thus although, typically, the composition will comprise thethree essential components, a fourth component, at least, can also bepresent. Typical further components include other fluorocarbons and, inparticular, hydrofluorocarbons, such as those having a boiling point atatmospheric pressure of at most −40° C., preferably at most −49° C.,especially those where the F/H ratio in the molecule is at least 1,preferably R23, trifluoromethane and, most preferably, R32,difluoromethane. In general, the maximum concentration of these otheringredients does not exceed 10% and especially not exceeding 5% and moreespecially not exceeding 2%, by weight, based on the sum of the weightsof components (a), (b) and (c). The presence of hydrofluorocarbonsgenerally has a neutral effect on the desired properties of theformulation. Desirably one or more butanes, especially n-butane oriso-butane, represents at least 70%, preferably at least 80% and morepreferably at least 90%, by weight of the total weight of hydrocarbonsin the composition. It will be appreciated that it is preferable toavoid perhalocarbons so as to minimize any greenhouse effect and toavoid hydrohalogenocarbons with one or more halogens heavier thanfluorine. The total amount of such halocarbons should advantageously notexceed 2%, especially 1% and more preferably 0.5%, by weight.

According to a preferred embodiment, the composition comprises, ascomponent (a) 62 to 67% based on the weight of the composition ofpentafluoroethane, as component (b) 3 to 35% by weight based on theweight of the composition of 1,1,1,2-tetrafluoroethane and, as component(c), butane and/or isobutane or a said mixture of hydrocarbonscomprising butane and/or isobutane. When component (c) is a mixture theconcentration of butane and/or isobutane in the mixture is preferably atleast 50% by weight especially at least 70% by weight, more preferablyat least 80% by weight and even more preferably at least 90% by weight,based on the weight of the composition. The other component of themixture is preferably pentane.

It has been found that the compositions of the present invention arehighly compatible with the mineral oil lubricants which have beenconventionally used with CFC refrigerants. Accordingly the compositionsof the present invention can be used not only with fully syntheticlubricants such as polyol esters (POE), polyalkyleneglycols (PAG) andpolyoxypropylene glycols or with fluorinated oil as disclosed inEP-A-399817 but also with mineral oil and alkyl benzene lubricantsincluding naphthenic oils, paraffin oils and silicone oils and mixturesof such oils and lubricants with fully synthetic lubricants andfluorinated oil.

The usual additives can be used including “extreme pressure” andantiwear additives, oxidation and thermal stability improvers, corrosioninhibitors, viscosity index improvers, pour point depressants,detergents, anti-foaming agents and viscosity adjusters. Examples ofsuitable additives are included in Table D in U.S. Pat. No. 4,755,316.

The following Examples further illustrate the present invention.

EXAMPLES

The samples used for testing are detailed below:

Butane (3.5%) blend: R125/134a/600 (65.0/31.5/3.5)Isobutane (3.5%) blend R125/134a/600a (64.9/31.7/3.4)

Equipment and Experimental

The samples, each approximately 600 g, used for the determination of thevapour pressures were prepared in aluminum disposable cans(Drukenbehalter—product 3469), which were then fully submerged in athermostatically controlled water bath. For each determination the canwas charged with about 600 g. A maximum of two samples could beprocessed at any one time. The bath temperature was measured using acalibrated platinum resistance thermometer (152777/1 B) connected to acalibrated Isotech TTI1 indicator. Pressure readings were taken usingthe two calibrated Druck pressure transducers, DR1 and DR2.

The temperature of the bath was set to the lowest temperature requiredand it was then left until it had cooled. When the temperature andpressure had remained constant for at least a quarter of an hour theywere then recorded. Further temperature and pressure readings were takenin increments of 5° C. to a maximum of 50° C., each time ensuring thatthey were steady for at least a quarter of an hour before recordingthem.

The data obtained does not give the dew point and as such does not givethe glide. An approximate evaluation of the glide can be obtained byusing the REFPROP 6 program. The relationship of the glide to the bubblepoint can be represented by a polynomial equation. This equation can nowbe used to give an approximate glide for the experimentally determinedbubble points. This is effectively a normalization of the calculatedglide to the experimentally determined data. The dew point pressures canthen be approximated by subtracting the temperature glide from thetemperature in the bubble point equation.

These equations are then used to obtain vapour/pressure tables. Theexperimental equation derived for the bubble points and the glideequation from REFPROP 6 are shown in Table 1.

Notes:

-   -   1. In this equation x=1/T, where T is the bubble point in        Kelvin: y=ln(p), where p is the saturated vapour pressure in        psia. To convert psia to MPa absolute pressure, multiply by        0.006895.    -   2. In this equation x=t, where t is the liquid temperature        (bubble point) in degree C. and y—glide in degree C. at the        bubble point temperature.    -   3. The vapour pressures for R22 were obtained from the Ashrae        handbook by interpolation.

Determination of the Performance of the Refrigerants on the LowTemperature (LT) Calorimeter.

Equipment and General Operating Conditions

The performance of the refrigerants was determined on the lowtemperature (LT) calorimeter. The LT calorimeter is fitted with a Bitzersemi-hermetic condensing unit containing Shell SD oil. The hot vapourpasses out of the compressor, through an oil separator and into thecondenser. The discharge pressure at the exit of the compressor is keptconstant by the means of a packed gland shut-off valve. This inevitablyhas an effect on the condensing pressure/temperature—the system isactually condensing at a temperature below 40° C. The refrigerant thentravels along the liquid line to the evaporator.

The evaporator is constructed from 15 mm Cu tubing coiled around theedges of a well-insulated 32-litre SS bath. The bath is filled with50:50 glycol:water solution and heat is supplied to it by 3×1 kW heaterscontrolled by a PID controller. A stirrer with a large paddle ensuresthat the heat is evenly distributed. The evaporating pressure iscontrolled by an automatic expansion valve.

The refrigerant vapour returns to the compressor through a suction lineheat exchanger.

Twelve temperature readings, five pressure readings, compressor powerand heat input are all recorded automatically using Dasylab.

The tests were run at a condensing temperature of 40° C. and anevaporator superheat of 8° C. (±0.5° C.).

For R22 the temperature at the end of the evaporator was maintained at8° C. above the temperature equivalent to the evaporating pressure(bubble point).

For the other refrigerants the temperature at the end of the evaporatorwas maintained at 8° C. above the temperature equivalent to theevaporating pressure (Dew point).

The mean evaporator temperature for these refrigerants was calculated bytaking the temperature equivalent to the evaporator pressure from thebubble point table and adding to that half the glide at the temperature.

When running the calorimeter the evaporating and condensing pressuresare initially set to an approximate value along with the temperature ofthe bath. The calorimeter is then allowed time for the conditions tostabilise. During this period coarse adjustments can be carried out andit must also be monitored in order to make sure that sufficient heat isbeing put into the bath to avoid any liquid getting back to thecompressor. When the system is virtually steady fine adjustments ofpressure and temperature are made until the calorimeter has stabilisedat the required evaporating pressure with a condensing pressureequivalent to 40° C. and an evaporator superheat of 8° C. (Note—thesuperheat is measured from the third evaporator outlet.)

The run is then commenced and run for a period of one hour, during whichtime no adjustments are made to the system, except for possibly minorchanges to the condensing pressure to compensate for fluctuations in theambient temperature.

Specific Experimental Details for each Refrigerant

R22: The calorimeter was charged with R22 (3.5 kg into the liquidreceiver). Ten data points were obtained between the evaporatingtemperatures of −38° C. and −22° C.

Butane (3.5%) blend: Approximately 3.55 kg were charged into the liquidreceiver and five data points were obtained between the mean evaporatingtemperatures of −38° C. and −22° C.

Isobutane (3.5%) blend: Approximately 3.48 kg of the blend were chargedinto the liquid receiver of the LT-calorimeter. Five data points betweenthe mean evaporating temperatures of −38° C. and −22° C. were obtained.

Results

The results obtained are summarised in Tables 2-4. Mean Ev. Temp=Meanevaporation temperature; Air on condenser=temperature of the air blowingover the condenser; Press=pressure.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a graph comparing the saturated vapour pressure of selectedblends with that of R22.

FIG. 2 is a graph comparing the capacity of selected blends with that ofR22 at a mean evaporating temperature of −30° C.

FIG. 3 is a graph comparing the percentage deviation in COP of selectedblends with that of R22 at a mean evaporating temperature of −30° C.

FIG. 4 is a graph comparing the COPs at a constant capacity (fixed forR22) for selected blends at the evaporating temperature of −30° C.

FIG. 5 is a graph showing the capacity of selected hydrocarbon blendsrelative to R22.

FIG. 6 is a graph showing the percentage deviation in COP of selectedblends relative to R22 over a range of evaporating temperatures.

COMMENTS AND DISCUSSION ON THE EXPERIMENTAL RESULTS

The results obtained are shown graphically in Graphs 1 to 6. Graph 1shows the saturated vapour pressures for the blends investigated alongwith that for R22. The graph shows that the vapour pressures of theblends are only slightly higher than that for R22.

Graph 2 shows a comparison of the capacities with respect to R22 at amean evaporating temperature of −30° C.—a typical temperature at whichthese blends would be expected to operate. At this temperature thebutane blend is only 4% down on capacity against R22, whereas thecapacity of isobutane blend is slightly inferior, being 5.5% down onR22.

The COP results obtained are shown in Graph 3. This graph shows that ata mean evaporating temperature of −30° C. the COP values of both thehydrocarbon blends are less than 1% down on R22.

In Graph 4, the capacity is fixed to that of R22 at the evaporatingtemperature of −30° C. The COPs at this constant capacity for thedifferent refrigerants can now be compared. The graph shows that boththe butane blend (by 2.5%) and the isobutane blend (by 3.0%) are moreefficient than R22 for this given capacity.

The capacity of the hydrocarbon blends relative to R22 is shown in Graph5. The lines for the two blends are parallel to one another and thecapacities are similar with that of the isobutane blend being slightlyinferior.

Graph 6 shows the COP of the RX blends relative to R22. The COP of R22and that of the two blends is shown to be similar. The lines of thehydrocarbons blends cross over one another (and R22) at a meanevaporating temperature of -32° C. showing the increase in the relativeCOP of R22 and the decrease in the relative COP of the isobutane blend.As before though the differences are only minimal.

TABLE 1 Results of the Experimental SVP Measurements and the glide fromREFPROP 6 SVP Equation Glide equation Description (see note 1) (see note2) Butane (3.5%) blend y = −2347.46820x + y = −0.02618x + R125/134a/60012.96325 3.51740 (65.0/31.5/3.5) R² = 0.99999 R² = 0.99790 Isobutane(3.5%) blend y = −2356.045324x + Y = −000001x³ − R125/134a/600a 129997290.000012x² − (64.9/31.7/3.4) R² = 0.999956 0.028998x + 3.628716 R22 (seenote 3) Not applicable

TABLE 2 R22 CONDENSING AT 40° C. IN LT−CALORIMETER Mean DischargeEvaporator Evap Evap Capacity Ev. Discharge Air On absolute CondensingInlet Temp Temp Compressor Heat Evap. Temp Temp Condenser Press TempPress BUBBLE DEW Power Input Superheat ° C. ° C. ° C. Mpa ° C. MPa ° C.° C. kwh kwh C.O.P. ° C. −37.6 149.9 20.8 1.439 40.1 0.016 −37.6 −37.61.161 0.614 0.53 8.3 −35.9 154.5 22.3 1.425 39.8 0.025 −35.9 −35.9 1.2080.846 0.70 8.5 −34.0 156.1 22.2 1.433 40.0 0.036 −34.0 −34.0 1.283 1.0310.80 8.3 −31.6 156.3 22.9 1.438 40.1 0.051 −31.6 −31.6 1.375 1.282 0.938.3 −29.5 155.7 23.4 1.450 40.4 0.065 −29.5 −29.5 1.388 1.412 1.02 7.8−28.8 152.8 22.0 1.447 40.4 0.071 −28.8 −28.8 1.418 1.508 1.06 8.1 −28.1154.7 23.9 1.430 39.9 0.076 −28.1 −28.1 1.457 1.586 1.09 8.4 −25.4 152.722.7 1.449 40.4 0.096 −25.4 −25.4 1.593 1.992 1.25 8.0 −24.0 152.8 23.81.446 40.3 0.108 −24.0 −24.0 1.646 2.167 1.32 8.6 −22.1 149.6 23.8 1.45040.4 0.124 −22.1 −22.1 1.688 2.387 1.41 8.4

TABLE 3 BUTANE (3.5%) CONDENSING AT 40° C. IN LT−CALORIMETER EvaporatorMean Discharge Inlet Evap Evap Capacity Ev. Discharge Air On absoluteCondensing Absolute Temp Temp Compressor Heat Evap. Total Temp TempCondenser Press Temp Press BUBBLE DEW Power Input Superheat Superheat °C. ° C. ° C. Mpa ° C. MPa ° C. ° C. kwh kwh C.O.P. ° C. ° C. −37.4 114.120.8 1.528 39.9 0.025 −39.7 −35.1 1.094 0.629 0.58 7.7 47.0 −34.2 115.821.6 1.529 39.9 0.044 −36.4 −31.9 1.237 0.976 0.79 7.9 43.5 −30.4 112.121.1 1.539 40.2 0.068 −32.6 −28.3 1.336 1.317 0.99 7.8 39.7 −25.9 108.921.4 1.540 40.2 0.102 −28.0 −23.8 1.459 1.729 1.18 8.0 36.7 −22.5 106.822.6 1.543 40.3 0.132 −24.6 −20.4 1.592 2.161 1.36 8.3 35.5

TABLE 4 ISOBUTANE BLEND (3.5%) CONDENSING AT 40° C. IN LT−CALORIMETEREvaporator Mean Discharge Inlet Evap Evap Capacity Ev. Discharge Air Onabsolute Condensing Absolute Temp Temp Compressor Heat Evap. Total TempTemp Condenser Press Temp Press BUBBLE DEW Power Input SuperheatSuperheat ° C. ° C. ° C. Mpa ° C. MPa ° C. ° C. kwh kwh C.O.P. ° C. ° C.−37.7 114.6 23.1 1.544 40.0 0.023 −40.1 −35.3 1.033 0.596 0.58 8.0 49.0−34.3 116.2 23.2 1.544 39.9 0.043 −36.6 −31.9 1.194 0.950 0.80 8.3 44.8−29.8 113.1 22.2 1.544 40.0 0.072 −32.1 −27.5 1.353 1.361 1.01 8.5 40.1−26.2 109.7 22.4 1.538 39.8 0.100 −28.4 −23.9 1.440 1.682 1.17 8.6 37.7−21.5 106.4 24.2 1.562 40.4 0.140 −23.6 −19.3 1.622 2.252 1.39 8.2 35.4

1-25. (canceled)
 26. A refrigerant composition wherein the refrigerantcomponent consists essentially of: (a) pentafluoroethane in an amountfrom 60% to 70% by weight based on the weight of the refrigerantcomponent; (b) 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane or amixture thereof in an amount from 26% to 36% by weight based on theweight of the refrigerant component; and (c) from 1% to 4% by weightbased on the weight of the refrigerant component of ahydrocarbon-containing component selected from the group consisting ofisobutane, n-pentane, isopentane and mixtures thereof; (d) up to 2% byweight based on the weight of the composition of another fluorocarbonwherein the other fluorocarbon is selected from the group consisting oftrifluoromethane, difluoromethane and mixtures thereof; said refrigerantcomposition optionally comprising (e) at least one lubricant; andoptionally comprising (f) at least one additive selected from the groupconsisting of extreme pressure additives, antiwear additives, oxidationand thermal stability improvers, corrosion inhibitors, viscosity indeximprovers, pour point depressants, detergents, anti-foaming agents, andviscosity adjusters.
 27. The refrigerant composition of claim 26,wherein he weight ratio of component (a): component (b) is desirably atleast 1.5:1.
 28. The refrigerant composition of claim 26 consistingessentially of components (a), (b), (c), (d) and (e).
 29. Therefrigerant composition of claim 26 consisting essentially of components(a), (b), (c), (d), (e) and (f).
 30. The refrigerant composition ofclaim 26 consisting essentially of components (a), (b), (c) and (d). 31.The refrigerant composition of claim 26 consisting essentially ofcomponents (a), (b), (c) and (e).
 32. The refrigerant composition ofclaim 26 consisting essentially of components (a), (b), (c) and (f). 33.The refrigerant composition of claim 26 consisting essentially ofcomponents (a), (b) and (c).
 34. The refrigerant composition of claim 26wherein component (a) is present in an amount about 62% to about 67% byweight based on the weight of the composition.
 35. The refrigerantcomposition of claim 26 wherein component (b) is present in an amountabout 28% to about 32% by weight based on the weight of the composition.36. The refrigerant composition of claim 26 wherein component (e) ispresent and comprises at least one lubricant selected from the groupconsisting of mineral oils, alkylbenzene lubricants, syntheticlubricants, and fluorinated oils and mixtures thereof.
 37. Therefrigerant composition of claim 26 wherein component (b) is a mixtureof 1,1,1,2-tetrafluoroethane and 1,1,2,2-tetrafluoroethane and is atleast half 1,1,1,2-tetrafluoroethane.
 38. A refrigeration apparatuscontaining, as refrigerant, a refrigerant composition of claim 26.